package com.community.windy.util;

import org.apache.commons.lang3.CharUtils;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;


@Component
public class SensitiveFilter {

    private static final Logger logger = LoggerFactory.getLogger(SensitiveFilter.class);
    //替换符
    private static String REPLAYCEMENT ="****";

    //根节点
    private TrieNode rootNode = new TrieNode();

    //bean初始化时调用
    @PostConstruct
    public void init(){
        try (
                InputStream is = this.getClass().getClassLoader().getResourceAsStream("sensitive-words.txt");
                BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        ){
            String keyword;
            while ((keyword = reader.readLine())!=null){
                //添加到前缀树
                this.addKeyword(keyword);
            }
        }catch (IOException e){
            logger.error("加载敏感词文件失败: "+e.getMessage());
        }
    }
    //将一个敏感词添加到前缀树中
    private void addKeyword(String keyword){
        TrieNode tempNode = rootNode;
        for (int i=0;i<keyword.length();i++){
            char c = keyword.charAt(i);
            TrieNode sunNode = tempNode.getSubNode(c);

            if (sunNode == null){
                //初始化子节点
                sunNode = new TrieNode();
                tempNode.addSubNode(c,sunNode);
            }
            //指针指向子节点，进入下一轮循环
            tempNode = sunNode;
            //设置结束标识
            if (i==keyword.length()-1){
                tempNode.setKeywordEnd(true);
            }
        }
    }

    /**
     * 过滤敏感词
     * @param text 待过滤的文本
     * @return 过滤后的文本
     */
    public String filter(String text){
        if (StringUtils.isBlank(text)){
            return null;
        }
        //指针1
        TrieNode tempNode = rootNode;
        //指针2
        int begin = 0;
        //指针3
        int position =0;
        //结果
        StringBuilder sb = new StringBuilder();

        while (position<text.length()){
            Character c = text.charAt(position);
            //跳过符号
            if (isSymbol(c)){
                //若指针1处于根节点，将
                if (tempNode==rootNode){
                    sb.append(c);
                    begin++;
                }
                position++;
                continue;
            }
            //检查下级节点
            tempNode = tempNode.getSubNode(c);
            if (tempNode==null){
                //以 begin 开头的字符串不是敏感词
                sb.append(text.charAt(begin));
                //进入下一位置
                position = ++begin;
                //重新指向根节点。
                tempNode = rootNode;
            }else if (tempNode.isKeywordEnd()){
                sb.append(REPLAYCEMENT);
                //进入下一个位置;
                begin = ++position;
                //重新指向更节点
                tempNode = rootNode;
            }else {
                //检查下一个字符。
                if (position<text.length()-1){
                    position++;
                }
            }
        }
        //将最后一批字符计入结果
        sb.append(text.substring(begin));
        return sb.toString();
    }

    //判断是否为符号
    private boolean isSymbol(Character c){
        //0x2E80-0x9FFF 是东亚文字范围、
        return !CharUtils.isAsciiAlphanumeric(c)&&(c<0x2E80||c>0x9FFF);
    }

    //前缀数
    private class TrieNode{
        //关键词结束标识
        private boolean isKeywordEnd  = false;

        //子节点key是下级字符，value是下级节点。
        private Map<Character,TrieNode> subNodes = new HashMap<>();

        public boolean isKeywordEnd(){
            return isKeywordEnd;
        }

        public void setKeywordEnd(boolean keywordEnd){
            isKeywordEnd = keywordEnd;
        }

        //添加子节点
        public void addSubNode(Character c,TrieNode node){
            subNodes.put(c,node);
        }
        //获取子节点
        public TrieNode getSubNode(Character c){
            return subNodes.get(c);
        }
    }
}
